Head-mounted displays comprising display devices such as small liquid crystal display panels disposed inside a casing having the form of a pair of spectacles have been developed, and by wearing one of these head-mounted displays a user can enjoy virtual large-screen video. An example of a known optical system of a head-mounted display is shown in FIG. 1.
This FIG. 1 schematically shows an optical system from inside a head-mounted display as seen from the left side (from the side of the left ear of a user wearing the head-mounted display like spectacles); the left-right direction in the figure is the front-rear direction of the head-mounted display, which is positioned in front of the eyes of the user. The optical system includes a back light 71 and a liquid crystal panel 80 disposed horizontally at the top of the head-mounted display. The liquid crystal panel 80 has a display region 81 and an area occupied by a display driving circuit 82 for driving this display region 81.
Light of a video picture displayed by the liquid crystal panel 80 is reflected by a half mirror 72 onto a concave half mirror 73, and light reflected and enlarged by this concave half mirror 73 then passes through the half mirror 72 to the eyes of the user. A liquid crystal shutter 74 is disposed in front of the concave half mirror 73, and by switching this liquid crystal shutter 74 between a transparent state and a blocking state with respect to light from outside the user can as desired control between seeing to the outside through the head-mounted display while still wearing the head-mounted display (that is, seeing the scene outside together with the displayed picture) or seeing only the displayed picture.
If the display region 81 of the liquid crystal panel 80 has nxc3x97m pixels in the horizontal and vertical directions respectively, a dot scan shift register as a pixel driving circuit for driving n pixels arrayed in the horizontal direction and a line scan shift register for sequentially scanning m lines arrayed in the vertical direction are provided in the display driving circuit 82. FIG. 2B is an enlarged view of a part enclosed by the dashed circle in FIG. 2A and shows parts of the display region 81 and the display driving circuit 82.
If the liquid crystal panel 80 is a color panel then image data for each of the three colors R, G and B are supplied to it, and FIG. 2B shows the construction of a part corresponding to for example R image data in an example wherein as R image data three data are supplied to dot scan shift registers 82b, 82c and 82d in parallel. For example three consecutive data are inputted in parallel for reasons relating to image data transfer speed (dot clock frequency), shift register transfer speed, liquid crystal response speed and resolution and so on. Thus this case of three data parallel input is merely an example, and parallel inputting of four or more data or serial inputting with a single dot scan shift register are also conceivable.
These dot scan shift registers (82b, 82c, 82d) are provided for data of each of the colors R, G and B, and consequently the area of the circuit part occupied by the dot scan shift registers disposed in the horizontal direction above or below the display region 81 is relatively large. Although only R pixels are shown in FIG. 2B as the pixels of the display region 81, G pixels and B pixels are also similarly arrayed (in substantially the same positions) and driven by a dot scan shift register for G pixels and a dot scan shift register for B pixels.
A line scan shift register 82a is disposed as a driving circuit for vertical scanning on the left side or the right side of the display region 81. This line scan shift register 82a is used commonly for all the pixels of the colors R, G and B. That is, the line scan shift register 82a executes scanning wherein it successively activates one line of pixels at a time on the basis of a scanning signal generated from vertical and horizontal synchronizing signals, and the signal lines of these lines (pixel gate lines) are common to all the R, G and B pixels of each line.
The display driving circuit 82 thus made up of the dot scan shift registers 82b through 82d and the line scan shift register 82a necessitates a large area for circuit provision on the dot scan shift register side, i.e. in the vertical direction of the display region. That is, although only one single line scan shift register common to R, G and B is needed, because a dot scan shift register must be provided for each of the colors R, G and B at least three are necessary, and in the case of three data parallel inputting shown in FIG. 2B nine are necessary.
Here, in the head-mounted display described above, considering the need to make the display part positioned in front of the eyes of the user small and light and considering aesthetic design aspects, it is desirable for the head-mounted display to be made small in the front-rear direction.
To make the head-mounted display small in the front-rear direction, as can be seen from FIG. 1 it is necessary to reduce the front-rear direction dimensions of the back light 71 and the liquid crystal panel 80, which are disposed horizontally. However, although reducing the size of the back light 71 is not so difficult, reducing the size of the liquid crystal panel 80 in the front-rear direction (that is, the vertical direction of the screen as seen by the user) is difficult.
This will now be explained with reference to FIG. 2A. As mentioned above, for the dot scan shift registers to be disposed above or below the display region 81, the display driving circuit 82 requires a large area for example above the display region 81, as shown in FIG. 2A. Consequently, even if the size of the display region 81 is reduced as shown in FIG. 2A to reduce the front-rear direction size of the liquid crystal panel 80, because the size of the display driving circuit 82 in the vertical direction does not change, the front-rear direction size of the liquid crystal panel 80 cannot be effectively reduced.
Although it is conceivable to dispose the dot scan shift registers in a position on the left or on the right of the display region 81, because in this case the laying of signal lines to the many pixels lined up in the horizontal direction becomes extremely complicated and in the end also necessitates area in the vertical direction, it is not suitable means for solving the problem.
Thus because of the difficulty of reducing the size of the liquid crystal panel 80 in the vertical direction there has been the problem that it is not possible to realize size reduction of a head-mounted display in the front-rear direction.
It is therefore an object of the present invention to provide a display device with which it is possible to effectively realize size reduction in the vertical direction.
To achieve this and other objects, according to a first provision of the invention a display device comprises displaying means for, by having a line scan driving circuit disposed with respect to pixel rows of a horizontal direction of a display region and a pixel driving circuit (dot scan driving circuit) disposed with respect to pixel rows of a vertical direction of the display region, performing image display with pixel groups each forming one line in the vertical direction being scanned in the horizontal direction, vertical-horizontal converting means for converting an image data stream supplied presupposing n pixels in a horizontal direction and m horizontal lines in a vertical scanning direction into an image data stream for m pixels in a vertical direction and n vertical lines in a horizontal scanning direction, and display controlling circuit means for executing image display in the display region of the displaying means by carrying out predetermined processing on and supplying to the pixel driving circuit of the displaying means image data outputted from the vertical-horizontal converting means and supplying a horizontal direction scanning signal synchronized with that image data to the line scan driving circuit. That is, image data is supplied to the displaying means as vertical-horizontal converted data streams and a display operation is executed by vertical pixel rows being scanned in the horizontal direction. In this case, because the line scan driving circuit is disposed above or below the display region, the area required for circuit provision above or below the display region is reduced.
In a second provision of the invention, the vertical-horizontal converting means converts RGB color image data streams supplied presupposing n pixels in a horizontal direction and m horizontal lines in a vertical scanning direction into RGB image data streams for m pixels in a vertical direction and n vertical lines in a horizontal scanning direction and outputs these RGB image data streams color-sequentially using time division. Also, the displaying means is a transmitting or reflecting monochrome liquid crystal display panel, and for display operation of this monochrome liquid crystal display panel an RGB color back light or an RGB color front light carries out a light-emitting operation RGB color-sequentially in correspondence with the RGB image data streams color-sequentially outputted from the vertical-horizontal converting means. In this case, color display is possible with displaying means having ⅓ the number of pixels of an RGB color liquid crystal panel. Or, put another way, in a liquid crystal panel of the same size, the number of pixels can effectively be tripled and high resolution thereby achieved.
According to another provision of the invention, by two units of the displaying means being disposed left-right symmetrically and the display controlling means supplying image data and scanning signals to these two displaying means so that they display the same image while mutually inverted in a top-bottom direction and in a left-right direction, it is possible to raise the freedom of configuration design of for example a head-mounted display or the like.
With the first provision of the invention described above, because a data stream obtained by vertical-horizontal converting ordinary image data by means of vertical-horizontal converting means is supplied to the displaying means and the display operation is executed by vertical pixel rows being scanned in the horizontal direction, it becomes natural for the line scan driving circuit to be disposed above or below the display region in the displaying means. In other words, it becomes unnecessary for a pixel driving circuit requiring a large area for circuit provision to be disposed above or below the display region, and as a result there is the effect that it becomes possible to effectively reduce the size of the displaying means in the vertical direction. And when the display device is to be mounted in a head-mounted display, this makes it possible to reduce the size of the head-mounted display in the front-rear direction.
Color display can be realized according to this provision of the invention by the displaying means being made a transmitting or reflecting color liquid crystal display panel and there being provided a white back light or a white front light for display operation of this color liquid crystal display panel.
In the second provision of the invention described above, vertical-horizontal converting means converts RGB color image data streams supplied presupposing n pixels in a horizontal direction and m horizontal lines in a vertical scanning direction into RGB image data streams for m pixels in a vertical direction and n vertical lines in a horizontal scanning direction and outputs these RGB image data streams color-sequentially using time division. Also, the displaying means is a transmitting or reflecting monochrome liquid crystal display panel, and for display operation of this monochrome liquid crystal display panel an RGB color back light or an RGB color front light carries out a lighting operation RGB color-sequentially in correspondence with the RGB image data streams color-sequentially outputted from the vertical-horizontal converting means. In this case, displaying means having the same resolution as an RGB color liquid crystal display panel can have ⅓ of the pixels, and there is the effect that it is possible to realize simplification of the circuit construction and accompanying reduction in size of the displaying means. Or, considering displaying means the same size (having the same total number of pixels) as an RGB color liquid crystal display panel, because effectively the number of pixels is tripled, there is the effect that high resolution can be achieved.
When according to the other provision of the invention mentioned above two units of the displaying means are disposed left-right symmetrically and the display controlling means supplies image data and scanning signals to these two displaying means so that they display the same image while mutually inverted in a top-bottom direction and in a left-right direction, there is the effect that it is possible to raise the freedom of configuration design of for example a head-mounted display or the like.